Dispersion of olefines in acid polymerization



Patented Sept. 27, 1938 DISPERSION OLEFINES IN ACID POLY MERIZATION IBruno E. Roetheli 'and- Eldon E. Stahly, Baton.

Rouge, La., assignors to Standard Oil Development Company, a corporationof Delaware Application October 24, 1936, Serial No. 107,322 7 Claims.(01. 196-10) The present invention relates to an improved process forproducing polymers suitable for motor fuels and motor fuel constituentsfrom normally gaseous .olefines, and more specifically to an improvedmethod for effecting such polymerization with sulfuric acid. The methodwill be fully understood from the following description and the drawing.

Referring to the drawing, Fig. 1 shows a sectional elevation of anapparatus for effecting polymerization or condensation of normallygaseous olefines by means of sulfuric acid and the flow of materialthrough the apparatus is indicated. Fig. 2 is a top cross-sectional viewof the apparatus shown in Fig. 1 taken along the line X-X. Figs. 3 and 4are larger scale drawings of the jets which are used to force theolefinic material to be polymerized into the reaction chamber.

2 The polymerizing action of sulfuric acid has been long known, and morerecently it has been employed to eifect the polymerization of liquefiednormally gaseous olefines, especially isobutylene, to form dimers andtrimers which are well suited, especially after hydrogenation, for useas motor fuels or for constituents of motor fuels. The present inventionis an improved method for carrying out this reaction and relatedcondensations between various oleflnes.

Turning to the drawing, in Fig. l the numeral I denotes a feed line bywhich the liquid olefines such as isobutylene or mixtures of isobutylenewith propylene, normal butylenes, amylenes or other olefines are forcedby means of the feed pump 2. The feed passes through one or the other ofthe two fine mesh screen filters 3 and 4 which are suitably fitted withvalved connections so that the one may be'cleaned while the other is inuse. into?" the lower portion of the polymerization chamber 6, intowhich it is discharged at a high velocity through a plurality of jets I,which will be 1 jacket 8. for heating, but it will'be understoodthatother heating means may be employed if de- 50 tain a relatively deepbath of sulfuric acid, and

therefore it should be constructed of materials capable of withstandingits corrosive action. The diameter of the chamber is determined by the56 number of jets required. It should be of sum- The material thenpasses by a pipe 5 sired. The reaction chamber is adapted to maincientheight to hold at' least 3 ft. of acid when measured in the quiescentstate, and it will be understood that the level will rise considerablythereafter when the olefine ispassed into the material so that the totalheight of the chamber should be at least 5 ft. and. preferably about 12ft.

A pipe 9 is provided at the upper end of the chamber for the withdrawalof the mixture of acid and olefine. Pipe 8 may be jacketed with anelement 2| in whicha cooling fiuid may be circulated to maintain auniform temperature of the exit materials or to cool the; same. Pipe 9discharges into the settling drum 22, which drum is connected by meansof line 23 to vent line l8.

A cooler in is provided to reduce the temperature of the mixture as itflows from the settling drum Settling drum 22 22 to the'separation drumII. is also provided with a draw-off line 24.

In the separation drum theacid and the hydrocarbon materials are allowedto stratify; the acid being heavier is found in the lower layer. This isremoved by a pipe I2 and recirculated to pump iii to the bottom of thepolymerization chamber.'

product from vessel i6 may be recirculated by,

pipe l9 and pump 20.

- Figs. 3 and 4'illustrate the preferred type of the jets I mentioned inconnection with Figs. 1 and 2. These jets are preferably replaceable asshown and are in the form of wide tubes narrowed at the end to provide ahole of small diameter, so as to cause the liquid to attain an extremelyhigh velocity in passing into the acid bath. This type of constructionminimizes the pressure drop required for the operation. In Fig. 3 thejetis directed upwardly, which is the preferred form,

while in Fig. 4 the jet is directed downwardly against a plate la whichmay be the bottom of reaction vessel 6, or may be a separate member soplaced as to best receive the stream of hydrobreaking it up into tinydroplets.

From the above description of the apparatus,

the operation will be generally understood, but

being maintained at polymerizing strength andtemperature. With moredilute acids, somewhat carbon and reverse its flow, at the same timetion of the isobutylene with another olefine of the such .as propyleneorstraight chain type, butylene, higher temperatures of the order of 200to 300 F. are used. For non-selective polymerization of olefines oroleflne mixtures, temperatures from 300 to 500 F. are employed.Super-atmospheric pressures should be employed with elevatedtemperatures in order to maintain the normally gaseous hydrocarbons inthe liquid condition. Pressures of 300.600 lbs. per square inch areordinarily required at temperatures of 200-300 F.

The above conditions for the. polymerization are important, and arebroadly known in the prior art. It is necessary, however, to combinethese conditions with the following specifications in order to obtainthe best results. It has been found that a single jet may be employedeffectively, and in that case the reaction vessel is best between 6inches and 12 inches in diameter. For commercial operations it is moredesirable to use a plurality of jets in a reaction vessel of largerdiameter. The jet diameter may vary from about 0.010 to 0.15 inch andthe velocity at the throat of the jet should be of the order of at least40 feet per second. If the velocity is below this figure, or on theother hand, if the diameter of the jet is larger, the hydrocarbon tendsto issue in acontinuous stream and effective polymerization is notobtained. For example, the yield drops off very rapidly because of theloss of interi'acialv ished. If it is attempted to make this up byincreasing the height of the acid, it is found that an excessive amountof trimer results which is likewise unde'irable. As indicated before, ithas been found that these conditions can' be so balanced that anextremely effective polymeriza-* tion may be obtained with an acidheight of 3 to 10 feet for the higher temperatures. indicated above,200-500 FL, although it is preferred to provide from 5 to 11 feet and touse lower temperatures. This acid height, it will be understood,

reaction is to circulate the acid as shown in Fig. 1.

percentages of 3,4 dimethyl hexene 2.

The rate of flow of acid upwardly .through the reaction chamber properis relatively slow and the hydrocarbon droplets rise quite rapidlythrough the acid. The flow of the acid is rapidly increased at. the topof the reaction vessel so that the reaction is substantially stoppedwhen the mixture of acid and hydrocarbon leaves the reaction chamber bythe'exit pipe. This effect may be enhanced by cooling the mixture as itis withdrawn and if desired the withdrawal pipe may be packed withacid-resistant shapes so as to assist the coalescence of thehydrocarbon. The actual separation occurs in the drum from which theacid is withdrawn for recirculation and the polymer withdrawn forrecovery.

It has been found that by increasing the time of. contact byrecirculation of a part of the polymer by means of line I 9 and pump 20,other conditions being the same, the yield of the codimer of iso andnormal butylene is increased. Without such recirculation there is asubstantial proportion of 2,2,4 trimethyl pentene formed, apparently bypolymerization of isobutylene, but by recirculation this can be reducedand 2,2,3 trimethyl pentene substituted, apparently by thecopolymerization of iso with normal butylene. At the same time suchrecirculation allows polymerization of normal butylene to formappreciable Under the optimum conditions 'of acid height, strength,temperature and rate of flow through the orifice, this expedient is notabsolutely necessary in order to reach the theoretical codimer, butrecirculation is desirable where optimum conditions are not employed.

. Example 1 To illustrate the operation of the present invention, anoleiine mixture consisting mainly of isobutylene and normal butylenes,the latter being in excess, was forced through a jet into the bottom ofa bath of 60% sulfuric acid. The temperature of the bath was maintainedat 225 F. and a total pressure of 400 lbs. per square inch was employedto maintain the olefine in liquid condition. These conditions areadapted toform copolymers of the isobutylene with normal butylene, andthe most effective operation would be one in which a yield from 175to-200%,

' based on the isobu ylene entering, is obtained olefine was forced inat different feed rates. In

the table below, the feed rate, velocity at the jet orifice, the yieldof polymer based on the isobutylene originally present, are giventogether with the time of contact in minutes, estimated from the jetsize, feed rate and the like. These times of contact were also checkedagainst runs in which naphtha or o her like hydrocarbons were dispersedthrough acid in a glass vessel in which the operation could be put underdirect observation The acid in the quiescent Yield based Jet Jet Contactdiameter m mm 3 3?: velocity time Liters/tour Percent FL/uc Minute: 1.018 4 22. 2 l. 11 2 .018 8 44.4 1. 7i 3 018 14 180 77. 7 l. 82

noted that the time of contact was only 1.1 min-' utes and the yieldabout 129% based on the isobutylene, which means either that theconversion per passwas low and that while some copolymer was produced,it failed by far to reach the theoretically possible quantity. Analysisof the exit gas showed that 90% of the isobutylene in the feed had beenpolymerized together with 19% of the normal butylenes.

In the second run, twice as much of the olefine was fed through the jetas in the previous run.

The velocity here was therefore twice what it was before, and rose abovethe critical velocity of about 40 feet per second. In spite of the factthat the rate of flow had been increased twice over the previousrun,-the time of contact was also greatly increased due to the fact thatvery much smaller droplets were produced. There was substantially nocontinuous stream of they hydrocarbon and consequently very littlecoalescence. It will be noted that the yield of polymer rose to 160%based on the isobutylene. This increase is quite remarkable in that itis coupled with the fact that a more effective poly butylenes.

.closer to the theoretical copolymer.

'mer is obtained, that is to say, the polymerv is Analysis showed that92% of the isobutylene was absorbed from the feed together with 33% ofthe normal The increased throughput is very noticeable, for example, theoverall amount of polymer produced in the second run is about 2% timesas much as that produced in the first run.

In the third run the rate is even higher and thevelocity is well withinthe preferred range. .It will be noted that the polymer is even moreeffective because it approaches even more closely the theoreticalcopolymer. Analysis shows that 94% of thuisobutylene is converted alongwith 40% of the normal butylenes. The total polymer produced under theseconditionsis about five times as much per hour as is obtained under theslow rate of flow illustrated in Run No. 1.

Example 2 In the following experiments the same mixtures of iso andnormal olefines were used as in the prior examples but a larger jet sizewas employed and the acid height was raised. As .be-

fore the temperature was 225 F., pressure 400 lbs. per square inch.

Table I Run Acid Yield on Jet veloc- No. J Glam height Feed rateisobutylene ity Inches Feet Liters/hr. FL/uc.

1 0. 023 6. 5 12 163 43. 2 2 0.023 3. 0 v 12 134 43.2 3 0. 023 6. 5 18192 64. 8 4 O. 023 11. 0 18 201 64. 8 5 0. 023 3. O 24 156 86. 4 6 0.023 6. 5 24 187 86. 4

' 7 O. 023 11. 0 24 191 36. 4 8 O. 018 6. 5 12 188 67. 2 9 O. 018 3. 012 180 67. 2

These runs show first that the '11 foot acid head is preferable to the 3foot or 6.5 foot head. This is illustrated by comparison of Runs 1 to'7, although the improvement in the use of the 11 foot head over thatobtained with the 6.5 foot head is not very large, With the smallerjet,.018

of normal bu ylene.

inch in'diameter, 6 feet of acid appears to be perfectly satisfactory.

Runs 4 and '7 should be particularly noted as they appear to employ thebest combination of conditions. The polymer yield is very close to thattheoretically obtained by copolymerization of isobutylene with normalbutylene: moreover, the isobutylene was substantially completelyconverted to polymer.

Example 3 In order to further illustrate the eflect of the jet velocity,some further runs are included in the following table, beyond the rangesillustrated above.

To illus ratethe polymerization of a normal olefine by the aboveprocesses, thefollowing experiment was performed. The acid level was 3feet in height at a temperature of 225 F. sulfuric acid was used and thefeed comprised a liquefied butylene and butane. The feed contained about18.1% of normal butylene with less 7 than 25% of isobutylene. It was fedin liquid s ate through the jets having a diameter of .018

inch at a rate of 15 liters per hour, which corresponds to a jetvelocity of 53.7 feet per second.

The polymer produced amounted to 35.5% of the normal butylene containedin the feed and was based on an analysis of feed and exit products. Thepolymer consisted of about 86% dimer and 14% trimer, and began to boilat 79 F., 69%

distilled over at about 300 F. and in the distillation a recovery of 74%was obtained. The hydrogenated material had excellent blending value asan antidetonation agent.

Example 5 The following experiment was carried out to illus rate theprocess of copolymerizing olefines containing three and four carbonatoms.v The reactor was filled with 66% sulfuric acid at a temperatureof 200 F., under 600 pounds per square inch of pressure. The jet had adiameter of .018 inch and the velocity of the liquefied hydrocarbonthrough the jet was 43.2 feet per second. The analyses of the feed andthe exit materials were as followsi Fad I Exitgas Percent From theseanalyses it can be seen that 43% of the propylene present in the feed isextracted and converted to a polymer. 75% of the isobutylene present islikewise converted with 30% The product has a gravity of 55.0 A. P. I.and began boiling at 123 F.; at 335 F.; the aniline point was 34 F.;color 14% (R). 'From the distillation curve it appears a great manyindividual hydrocarbons are pres ent, showing a large number ofcombinations of the-propylene with butylene and isobutylene.

In subsequent experiments with various sized jets, it is foundthat aminimum acid height of 3 to 5 feet and a maximum of about 10 to 12 feetis preferable, especially for polymerization of isobutylene orcopolymerization of iso with normal trace of isobutylene escapes in theexit liquor and the polymer itself contains less than 10% of trimer.

The present invention is not to be limited to any 7 theory of theoperation nor to the reactions involved therein, nor to any particularacid strength, temperature, or the like, but only to the followingclaims in which it is desired to claim the invention as broadly as theprior art permits.

We claim:

1. In a process for polymerizing liquefied normally gaseous olefines bymeans of sulfuric acid to form polymers suitable for motor fuels, thesteps of maintaining a bath of sulfuric acid at polymerizing strengthand temperature, forcing the olefine mixture in a liquefied state intothe lower part of the acid bath through a minute diameter orifice at avelocity in excess of 40 feet per second, whereby the liquid olefine isdispersed in small droplets throughout the acid, permitting the dropletsto rise through the acid, the height thereof being adapted to providetime for a substantial reaction of the oleflnes, then separatinghydrocarbons from the acid and recovering the polymer.

2. In a process for polymerizing liquefied normally gaseous olefines bymeans of sulfuric acid to form polymers suitable for motor fuels, thesteps of maintaining a bath of sulfuric acid at polymerizing strengthand temperature, forcing the olefine mixture in a liquefied state intothe lower part of the acid bath through a minute diameter orifice havingan orifice size within the limts of 0.01 and 0.15 inch at a velocity inexcess of 40 feet per second, whereby the liquid olefine is dispersed insmall droplets throughout the acid, permitting the droplets to risethrough the acid, the height thereof being adapted to provide time for asubstantial reaction of the olefines, then separating hydrocarbons fromthe acid and recovering the polymer.

3. In a process for polymerizing liquefied normally gaseous olefines bymeans of sulfuric acid to form polymers suitable for motor fuels, thesteps,of maintaining a bath of sulfuric acid at polymerizing strengthand temperature, forcing the olefine mixture in a liquefied state intothe lower part of the acid baththrough a minute diameter orifice havingan orifice size within'the limits of 0.01 and 0.15 inchat a velocity inexcess of 40 feet per second, whereby the liquid olefine is dispersed insmall droplets throughout the' acid, permitting the droplets to risethrough the acid, the, height thereof being at from about 3 feet to 10feet when measured in the quiescent state, then separating hydrocarbonsfrom the acid and recovering the polymer.

' 4. In a process for the polymerization of a mixture of isoand normalolefines to produce polymers suitable for motor fuels, the improvedsteps which comprise maintaining'a bath of sulfuric acid at polymerizingstrength and temperature within the range of 50-80% and 200-300 F., re-

spectively, forcing the olefine through a jet of from 0.01 to 0.15 inchin diameter at a rate in excess of 40 feet per second and providing aheight of acid from about 3-10 feet when measured in a quiescent state,then separating the hydrocarbon from the acid and recovering the polymerfrom the hydrocarbon.

5. A process according to claim 4 in which the sulfuric acid is passedat a slow rate upwardly through the reaction zone, the mixture of acidand hydrocarbon withdrawn rapidly from the reaction zone into aseparation zone, and in which the acid is recirculated from theseparation zone i to the reaction zone.

6. In a process for polymerizing liquefied normally gaseous olefines bymeans of sulfuric acid to form polymers suitable for motor fuels, thestep of maintaining a ,bath of sulfuric acid at polymerizing strengthand temperatures, forcing the olefine mixture in a liquefied state intothe lower part of the acid bath through a minute diameter orifice at avelocity in the range from about 40 feet to feet per second, whereby theliquid olefine,

is dispersed in small droplets throughout the acid, permitting thedroplets to rise through the acid,

the height thereof being adapted to provide time,

for a substantial reaction of the olefines, then separating hydrocarbonsfrom. the acid and recovering the polymer. i

7. In a process for the polymerization of a mixture of iso and normalolefines to produce polymers suitable for motor fuels, the improvedsteps which comprise maintaining a bath of sulfuric acid at polymerizingstrength and temperature within the range of 50 to 80% and 200 to 300F., respectively, forcing the olefine through a jet of from 0.01 to 0.15inch at a ratein the ranged from 40 feet per second to 150 feet persecond and providing an acid height of from 3 to 10 feet when measuredin a quiescent state, then separating the hydrocarbon from the acid andrecovering the polymer from the hydrocarbon.

